This project was understaken to study mutagenesis using monospecific antibodies against the sperm specific enzyme, lactate dehydrogenase-C. A monospecific antibody has been prepared from rabbit antiserum that reacts with rat sperm and not with mouse sperm. Using this antibody in a sandwich fluorescent antibody technique, point mutations in the mouse sperm were detected in mice treated with mutagenic drugs: procarbazine, mitomycin C, and ethylnitrosourea. Monospecific antibodies to mouse LDH-C which do not react with human sperm have been purified. Using these antibodies on human sperm, it may be possible to measure mutations in human sperm.